North America makes entry into dino fatty league

73-tonne dino is US's biggest yet

Seems like Americans have been fatties for longer than we thought. The heaviest creature to have walked on land lived in New Mexico circa the Late Cretaceous period, according to an article by Montana State Uni researchers.

Until now Alamosaurus sanjuanensis was only thought to have lived in South America. But after palaeontologists turfed two vertebrae and a femur out of the desert in New Mexico's badlands back between 2003-6, scientists have been reassessing the geographical spread of the lumbering uber-dino. And it looks like it roamed about eating plants in North America as well as Brazil and Argentina. It also looks like the dino was a lot bigger than paleontologists had previously estimated.

Bone findings before 2003 suggested that only smallish 30 tonne (about 30,000kg) Alamosaurus sauropods lived in the United States. But Montana PhD student Denver Fowler says that the earlier bone discoveries most likely came from young sauropods and didn't show just how big the dinos could actually get. After studying the newly-unearthed fossilised vertebrae he has concluded that they come from a creature in the same league as the largest sauropod of all, the Argentinosaurus.

"We used to think that a fully grown Alamosaurus measured around 60 feet long and weighed about 30 tonnes, but a 2009 study by another MSU researcher, Dr Holly Woodward, found that a femur thought to belong to an adult was still growing," Fowler said. "This told us that Alamosaurus got even bigger, but we didn't imagine that it could get quite this big."

The Argentinosaurus also weighed about 73 tonnes and, until now, was widely considered to be the biggest dinosaur of all.

Although 73,000kg [about 73 ton] may seem extraordinarily large, Argentinosaurus and other derived giant titanosaurians had wide−gauge bodies and were probably considerably stockier than more basal titanosauriforms like Giraffatitan, although confirmation of this awaits discovery of more complete specimens.

Montana University says that the finding puts the US "back in the fight for the number 1 spot".

Denver also said that further studies were required to understand what sort of evolution allowed dinosaurs to become so big. ®